Apartment houses have been continuously constructed in Korea to solve overcrowding in large cities. The interlayer noise arising from these apartment houses has now become a critical social problem which requires an urgent solution. In recent years, studies applying numerical analysis techniques with respect to the structural type and floor plane have been carried out to effectively reduce the heavy weight impact noise, which is a cause for the interlayer noise. This study proposes analytical impact force models based on the actual measurement data regarding the heavy weight impact noise, which is mandatory input data for performing a numerical analysis. Additionally, the appropriateness of the proposed models has been verified through a comparative review with Korean standards. With the use of the proposed model, a numerical analysis has been conducted using a wall-type specimen, and a comparative analysis has been also performed with respect to the field measurement data. The applicability of the proposed model to the numerical analysis shows the possibility to resolve the interlayer noise problems numerically posing difficulties due to both the limited costs and time. Finally, it is expected that more information can be provided to resolve the interlayer noise problem based on the numerical analysis of various boundary conditions.
Compared to the bottom ash obtained by a water-cooling system (wBA), dry process bottom ash (dBA) makes hardly any unburnt carbon because of its stay time at the bottom of the boiler and contains less chloride because there is no contact with seawater. Accordingly, to identify the chemical stability of dBA as a lightweight aggregate for construction purposes, the chemical properties of dBA were evaluated through the following process of the reviewing engineering properties of a lightweight aggregate (LWA). Typically, river gravel and crushed gravel have been used as coarse aggregates due to their physical and chemical stability. The coal ash and LWA, however, have a variety of chemical compositions, and they have specific chemical properties including SO3, unburnt coal and heavy metal content. As the minimum requirement to use the coal ash and lightweight aggregate with various chemical properties for concrete aggregate, the loss on ignition, the SO3 content and the amount of chloride should be examined, and it is also necessary to examine heavy metal leaching even though it is not included in the standard specifications in Korea. Based on the results, it is believed that there are no significant physical and chemical problems using dBA as a lightweight aggregate for concrete.
There have been frequent cases of civil complaints and disputes in relation to floor impact noises over the years. To solve these issues, a substantial amount of sound resilient material is installed between the concrete slab and the foamed concrete during construction. A new place-type resilient material is made from cement, silica powder, sodium sulfate, expanded-polystyrene, anhydrite, fly ash, and acrylic polymer emulsion resin. Its physical characteristics such as density, compressive strength, dynamic stiffness, and remanent strain are analyzed to assess the acoustic performance of the material. The experimental results showed the density and the dynamic stiffness of the proposed resilient material is increased with proportional to the use of cement and silica powder due to the high contents of the raw materials. The remanent strain, related to the serviceability of a structure, is found to be inversely proportional to the density and strength. The amount of reduction in the heavyweight impact noise is significant in a material with high density, high strength, and low remanent strain. Finally, specimen no. R4, having the reduction level of 3 dB for impact ball and 1 dB for bang machine in the single number quantity level, respectively, is the best product to obtain overall acoustic performance.
There has been increased deconstruction and demolition of reinforced concrete structures due to the aging of the structures and redevelopment of urban areas resulting in the generation of massive amounts of construction. The production volume of waste concrete is projected to increase rapidly over 100 million tons by 2020. However, due to the high cement paste content, recycled aggregates have low density and high absorption ratio. They are mostly used for land reclamation purposes with low added value instead of multiple approaches. This study was performed to determine an effective method to remove cement paste from recycled aggregates by using the abrasion and substituting the process water with acidic water. The aim of this study is to analyze the quality of the recycled fine aggregates produced by a complex method and investigate the optimum manufacturing conditions for recycled fine aggregates based on the design of experiment. The experimental parameters considered were water ratio, coarse aggregate ratio, and abrasion time and, as a result of the experiment, data concerning the properties of recycled sand were obtained. It was found that high-quality recycled fine aggregates can be obtained with 8.57 min of abrasion-crusher time and a recycled coarse aggregate ratio of over 1.5.
CO2 emitted from building materials and the construction materials industry has reached about 67 million tons. Controls on the use of consumed fossil fuels and the reduction of emission gases are essential for the reduction of CO2 in the construction area as one reduces the second and third curing to emit CO2 in the construction materials industry. In this study, a new curing method was addressed by using a low energy curing admixture (LA) in order to exclude autoclave curing. The new curing method was applied to make panels. Then, its physical properties, depending on the mixed amount of fiber, type of fiber and mixed ratio of fiber, were observed. The type of fiber did not appear to be a main factor that affected strength, while the LA mixing ratio and mixing amount of fiber appeared to be major factors affecting the strength. Applying the proposed new curing method can reduce carbon and restrain the use of fossil fuels through a reduction of the second and third curing processes, which emit CO2 in the construction materials industry. Therefore, it will be helpful to reduce global warming.
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